The present invention relates to a diagnosis device for diagnosing loosening of a stator core of a rotary electrical machine and its diagnosis method.
In general, in a stator of a rotary electrical machine such as an electric generator or an electric motor, a stator core is configured by laminating thin electromagnetic steel sheets having, on its inner radial side, a space into which a coil is inserted and clamping the laminated electromagnetic steel sheets in the axial direction. Then, a coli is inserted into a coil insertion space on the inner radial side of the electromagnetic steel sheets and is connected outside the stator core.
In the stator core having such a configuration, insufficient clamping of the stator core may decrease a clamping specific pressure of the laminated electromagnetic steel sheets. Accordingly, the electromagnetic steel sheets vibrate, so that insulating layers coated on the surface of the electromagnetic steel sheets may be separated therefrom due to rubbing and beating between the electromagnetic steel sheets, causing an electrical connection to be established between the electromagnetic steel sheets. As a result, an eddy current is induced and, in the worst case, the stator core undergoes melting damage. In order to prevent this, it has been necessary not only to assembling the stator core while adequately controlling the stator core specific pressure in the manufacturing process, but also to periodically check/inspect the stator core specific pressure in a plant in operation. Conventionally, in this inspection, a jig having a thin knife-like shape is inserted in a gap between the electromagnetic steel sheets, and the clamping state of the stator core is sensuously judged by the insertion condition. However, the judgment depends on the feeling of individual inspectors, so that a lot of skill is required for the judgment. Further, the judgment varies between individuals, resulting in a variation of quality.
In order to cope with this problem, Japanese Patent Application Laid-Open Publication No. 2000-354353, the entire contend of which is incorporated herein by reference, discloses a method of quantitatively evaluating the clamping state of the stator core. This method inserts a torque wrench into the air duct portion which is generally provided for cooling of the stator core of a rotary electrical machine and measures a torque value indicated by the torque wrench and displacement amount of the stator core or torque wrench obtained at the time when the torque wrench is inserted into the stator core to thereby numerically evaluate the stator core specific pressure.
As described above, it is necessary to insert the torque wrench into the air duct portion in the method disclosed in Patent Document 1. However, the air duct of this type generally has a narrow width and therefore a torque wrench formed in an extremely thin shape is required. On the other hand, the clamping specific pressure of the stator core is extremely high, so that when such a torque wrench formed in an extremely thin shape is used, the toque wrench itself is deformed. As a result, a sufficient external force cannot be applied to the stator core, making it impossible to evaluate the stator core clamping pressure properly.
Further, the torque wrench can apply an external force only to a small portion of the stator core, so that the stator core clamping pressure that can be evaluated is limited to a small portion of the stator core, i.e., a portion in the vicinity of the outer surface of the stator core where the specific pressure becomes comparatively low. Therefore, measurement needs to be made at many portions. Further, it is likely that the actual measurement result is evaluated lower than the average specific pressure of the stator core with the result that the stator core is clamped with more force than required. Furthermore, in existing plant diagnosis, there is a case where even a problem-free machine is determined to be abnormal.
The present invention has been made to solve the above-mentioned problem, and an object thereof is to provide a stator core loosening diagnosis device and its diagnosis method capable of easily and quantitatively determining the clamping state of the entire stator core of a rotary electrical machine.